Polyurethane block elastomers

ABSTRACT

THE INVENTION PROVIDES NEW POLYURETHANE BLOCK ELASTOMERS OF GOOD MECHANICAL PROPERTIES AND RSISTANCE TO YELLOWING MADE BY CONDENSING BIS(4-ISOCYANATO-CYCLOHEXYL)METHANE WITH AN A,W-DIHYDROXY MACRODIOL AND COUPLING THE ISOCYANATE-TERMINATED PREPOLYMER OBTAINED WITH 3,3-BIS(AMINOMETHYL)-OXACYLOBUTANE.

United States Patent ice Patented 32325;

It is known that when the nitrogen atoms of the ure- 3,651,027 thane orurea groups present in these polymers are not POLYURETHANE BLOCKELASTOMERS directly bonded to aromatic rings, the resistance of the Jeanb y Fl'anceifissignol' to Rhone said polymers to sunlight is largelyimproved. Polyure- Poulenc Pans France 5 thane elastomers having such aconfiguration have how- No Drawing. Filed Feb. 7, 1969, Ser. No. 797,675

C] priority application France Feb 9 1968 ever aroused little interest,especially in the textile field,

aims Q S Q because, with the exception of their stability to light, IntCL cbs 22/24 their properties are generally poor. Furthermore they areU,s C], 260 75 NH 6 Cl i generally insoluble or sparingly soluble in theusual polar 10 solvents such as dimethylformamide and dimethylacetamide.The solubilityin dimethylformamide is an important factor industriallybecause it is particularly advantageous to use this solvent in thesolution spinning of this type of ABSTRACT OF THE DISCLOSURE Theinvention provides new polyurethane block elastoelastomel" mers of goodmechanical properties and resistance to polyurfithalle block elastolnefhave How e yellowing d b condensing bi (4-i l discovered WhlCh are verysoluble in dimethylformamlde hexynmethane i an macrodiol and and have acombinatlon of mechanical and physical propcoupling theisocyanate-terminated prepolymer obtained ewes Whlch allows t use Intexnle E Thus Y with 3,3 bis(aminomethyl)oxacyclobutane. have asoftening point above 200 C., a high elongation and tensile strength, aswell as as a low residual elongation.

Furthermore, when these elastomers are exposed to sunlight for aprolonged period, they practically preserve The Presflrlt inventionrelates to Polyurethane block their whiteness and their mechanicalproperties.

elastomers suitable for the manufacture of fibres, films Thepolyurethane block elastomers of the present invenand varnishes, and totheir preparation. tion essentially consist of units of formulae:

FormulaI CHI-CH2 CHz-CH3 -O-A0C O-NH-Cfi CH-CHg-CH CH-NH-C 0- CHz-CCHr-CH: )m and FormulaII CHz-CHg GHQ-CH2 NHCH2CCHzNHCONHCH CHCHz-CHGH-NH-C 0- C 3 CH1 CHrCfiz CH2C g k O )n Elastomers of the polyurethaneblock type are well in which in and n represent integers from 20 to 400and known products generally prepared by condensing an A is such thatHO-A-OH is a macrodiol having a excess of a diisocyanate with amacrodiol to form a premolecular Weight of 700 to 5000 and a meltingpoint bepolymer having terminal isocyanate groups, the molecules low 80C.

of which are coupled by means of difunctional com- According to theinvention these new polymers are pounds containing active hydrogenatoms. Such difuncobtained by reacting an excess ofbis(4-isocyanato-cyclotional compounds may for example be glycols,diamines, hexyDmethane with a macrodiol -H0AOH as aforeaminoalcohols ordihydrazides. Diamines are the most said to produce anisocyanate-terminated prepolymer, and usually employed coupling agents.then coupling the chains of this prepolymer with bis-3,3-

These elastomers, which inter alia possess polyurethane (aminoethyl)oxacyclobutane (or bis 3,3-aminomethyl) sequences and more generallypolyurea sequences, have oxetane to form a polymer in which the blocksof extremely diverse chemical, physical or mechanical Formula II areseparated from each other by the blocks properties depending on thenature of the diisocyanate of Formula I, the coupling reaction beingcarried out in and of the coupling agent used during their preparation.the presence of a solvent for the final polymer.

'In the majority of cases elastomers based on aromatic The macrodiolswhich are used in the invention are diisocyanates such as2,4-diisocyanato-toluene or 2,6- u,w-dihydroxy polymers having amolecular weight of diisocyanato-toluene or his(4-isocyanatophenyl)methane 700 to 5000, preferably 1400 to 3500, and amelting point are preferred because they generally have goodmechanibelow 80 C. such macrodiols can be polyesters having calproperties. However these elastomers suffer from an acid numberpreferably less than 10. These polyesters a very serious defect. Whenexposed to sunlight they are generally obtained by reaction of one ormore caryellow very rapidly and this has the consequence of greatlyboxylic diacids with an appropriate amount of one or reducing their usein the filament and fibre field, particumore dialcohols. Among the mostcommonly used diacids, larly if textile articles, which keep theirwhiteness for may be mentioned aliphatic diacids such as succinic acid,the greatest part of their use, are desired. Furthermore this glutaricacid, adipic acid, pimelic acid, suberic acid, colour change isgenerally accompanied by a degradation azelaic acid and sebacic acid;cycloaliphatic diacids such of the polymer which results in asignificant deterioration as 1,4-cyclohexanedicarboxylic acid; andaromatic acids inits mechanical properties. such as ortho phthalic,isophthalic and terphthalic acids.

In order to reduce these disadvantages it has been As examples ofdialcohols, may be mentioned: 1,2- proposed to add various kinds ofstabilisers to these elastoethanediol, 1,2- and 1,3-propanediols, 1,2-,1,3-, and 1,4-

mers but in general these substances only provide a very butanediols,1,5-pentanediol, 1,6-hexanediol, 1,10-decinadequate protection which isrestricted in duration. It anediol and 2,=2-dimethyl-propane-1,3-diol.

is also frequently observed that if these agents raise the Anothermethod of producing an u,w-dihydroxy polygeneral level of certainproperties, they frequently also ester consists in subjecting a lactoneto polycondensation cause a marked alteration in mechanical properties.in the presence of a dialcohol.

It is also possible to use a,w-dihydroxy-polyethers obtained bypolycondensation of alkylene oxides, by themselves or conjointly withdialcohols. Suitable alkylene oxides include ethylene oxide, propyleneoxide and tetrahydrofuran.

u,w-Dihydroxy polyester-amides and a,w-dihydroxy polyurethanes ormacrodiols having carbon chains possessing a hydroxyl group at each endof the chain, such as a,w-dihydroxy polybutadienes andbutadiene-isobutylene copolymers can also be used in the presentinvention.

The bis(4-isocyanato-cyclohexyl)methane used in the preparation of theelastomers of the invention may be a mixture of varying amounts oftrans-trans, cis-trans and cis-cis isomers. Thus the product obtained byphosgenation of the bis(4-aminocyclohexyl)methane, the latter beingproduced by catalytic hydrogenation of the bis(4- aminophenyl)methane,is perfectly suitable. This product contains an average of 60 to 80parts of trans-trans isomer per 40 to 20 parts of cis-trans isomer, theamount of ciscis isomer being negligible.

The preparation of the prepolymer with terminal isocyanate groups iscarried out by reacting the macrodiol with thebis(4-isocyanato-cyclohexyl)methane at the rate of one molecule ofmacrodiol per 1.5 to 3, preferably 2, molecules of diisocyanate. Theoperation is carried out at a temperature not exceeding 150 C.,preferably between 100 and 130 C., optionally in the presence of aninert, anhydrous solvent such as toluene, for the time required to reactat least 95% of the hydroxyl groups.

The bis(4 isocyanato-cyclohexyl)methane can be added all at once at thebeginning of the operation but it is also possible only to use afraction of the chosen amount of diisocyanate initially, for examplebetween about 1.1 and 1.8 mols per 1 mol of macrodiol, and then to addthe rest of the diisocyanate during the heating. This latter process incertain cases makes it possible to improve the properties of theelastomer and especially to reduce the residual elongation.

Coupling between the chains of the prepolymer prepared in this way iseffected with 3,3-bis(aminomethyl)- oxetane. This diamine can be veryeasily obtained from pentaerythritol by the method of Campbell J. Org.Chem. 22, 1029 (1957). The diamine is preferably employed as a solutionin a solvent which is inert under the working conditions, and thereaction is carried out in the presence of a solvent for the finalpolymer, preferably at ordinary temperature. Suitable solvents for thefinal polymer include dimethylformamide, 1,1,3,3-tetramethylurea, N-methylpyrrolidone, dimethylsulphoxide, and tris(dimethylamino) phosphineoxide. Among these, it is particularly advantageous to usedimethylformamide.

The coupling reaction can be carried out by adding the diamine to theprepolymer or vice versa. If the diamine is introduced into theprepolymer, a premature rise in the viscosity at the end of the reactioncan be avoided by adding a small amount of an aliphatic monoamine whichpreferably has a boiling point below 180 C. under normal atmosphericpressure.

The total amount of amine employed [3,3-bis (aminomethyl)oxetane andoptionally, monoamine] corresponds to a number of amine groupsrepresenting about 100 to 105% of the number of isocyanate groups of theprepolymer, with the amine groups introduced by the ptional use of amonoamine representing at most 5% of the total number of amine groups.

The polyurethane block elastomers produced in accordance with theinvention may be obtained as concentrated solutions indimethylformamide, for example containing more than 30% by weight ofpolymer. These solutions have a viscosity which does not change withtime. They can be used for the formation of filaments by known dryspinning or wet spinning processes, after optional addition of variousfillers, the use of which is well known in the art. In this respect,white pigments, such as zinc 4 oxide or titanium oxide may be moreespecially mentioned.

The examples which follow illustrate the invention. The variousmechanical properties quoted in these examples are determined inaccordance with French Standard AFN OR T 46 002.

EXAMPLE 1 81.1 g. of toluene and 89.6 g. of a polyester (molecularweight 1791, acid number 1.4, hydroxyl number 61.1, melting point 3536C., obtained by esterification of a mixture of 1,6-hexanediol and2,2-dimethyl-propane-1,3'- diol, the molecular ratio of the dialcoholsbeing :20, with adipic acid) are introduced into an 0.5 l. borosilicateglass flask.

36.5 g. of toluene are distilled off to dehydrate the mixture and 26.2g. of bis(4-isocyanato-cyclohexyl)methane (M.P. about 60 C.) dissolvedin 36.5 g. of anhydrous toluene, are then added to the solution at C.The mixture is heated under reflux for 2 hours, and, after cooling, aprepolymer solution containing 0.0504 isocyanate groups per 100 g. ofsolution is obtained. V

44 g. of the prepolymer solution diluted with 73 cm. ofdimethylformamide are introduced into a cylindrical reactor of 250 cm.capacity placed under a nitrogen atmosphere, and a solution of 1.306 g.of 3,3-bis(aminomethyl)-oxetane in 39 cm. of dimethylformamide is addedover the course of 30 minutes with good stirring. A limpid, homogeneoussolution of viscosity 20 poises at 25 C. is obtained, whichis cast at athickness of 0.5 mm. After drying at C. for 2 hours, a film is obtainedwhich'has the following mechanical and physical properties:

Tensile strength-618 kg./cm.

Elongation at break-603% Force for 100% elongation-45 lrg./cm.

lmgnggate residual elongation after 100% elongation- Softening point200C.

The light resistance of the film is also measured with the Xenotest 450apparatus. In this apparatus the film is subjected to irradiation fromxenon lamp which gives a spectrum the composition of which is close tothat of sunlight. After 200 hours exposure, the whiteness of the film isidentical to that of a sample which has not been subjected toirradiation.

EXAMPLE 2 333 g. of toluene and 370 g. of a polyester (molecular weight1850, acid number 1.2, hydroxyl number 59.4,

melting point 29 0., obtained by esterification of a mix-v ture of1,6-hexanediol and 2,2-dimethyl-propane-1,3-diol, the molecular ratio ofthe diols being 66:34, with adipic acid) are introduced into a 2 l.borosilicate glass flask.

253 g. of toluene are distilled oil to dehydrate the mixture and 74.1 g.of bis(4-isocyanato-cyclohexyl)methane dissolved in 200 g. of anhydroustoluene are then added to the solution at about 100 C. The mixture isheated under reflux for 45 minutes, 31.7 g. of bis(4-isocyanatecyclohexyl)methane dissolved in 54 g. of anhydrous tolu-. ene are added,and the mixture is then again kept under parts. The first part isconcentrated to a polymer content of 28% by evaporation at 60-70 C.under a pressure of 4 mm. Hg. A limpid solution is thus obtained, theviscosity of which did not vary after one months storage at ambienttemperature (about 25 C.).

The second part is converted into a film as indicated in Example 1. Thisfilm has the following characteristics:

Tensile strength-664 l g./cm.

Elongation at break- 87% Force for 100% elongation-47.5 kg./cm.

Immediate residual elongation after 100% elongation- Softening point2l0C.

EXAMPLE 3 The procedure of the preceding example is followed, using589.5 g. of a solution of prepolymer containing 0.0495 isocyanate groupsper 100 g. of solution, 17.58 g. of 3,3-bis(aminomethyl)-oxetane and1600 cm. of dimethylformamide. A solution containing 17.2% by weight ofpolymer is obtained, into which 5% by weight of titanium dioxide, basedon the polymer, are introduced. 732 g. of solvent are then removed bydistillation at 6070 C CH2 C. under a pressure of 4 mm. Hg. Theresulting solution has a viscosity of 355 poises at C..and a solidscontent of 27.7%. This solution is extruded through a spinneret having13 holes of 0.15 mm. diameter into a coagulation bath containing amixture of water and dimethylformamide (ratio 25:75 by volume) kept at25 C.

A filament of 260 deniers gauge is obtained which, after washing andthen drying for /2 an hour at 150 C., has a tensile strength of 0.9g./denier and an elongation at break of 710%.

EXAMPLE 4 325 g. of toluene and 358 g. of a polyester (molecular weight1790, acid number 0.9, hydroxyl number 61.6, melting point below 25 0.,obtained by esterification of 1,2-ethanedi0l with a mixture of adipicacid and azelaic acid, the molecular ratio of the diacids being 50:50)are introduced into a borosilicate glass flask of 2 1. capacity.

The procedure of Example 1 is then followed, to yield a solution ofprepolymer containing 0.0534 isocyanate groups per 100 g. of solution.The operation is continued as described in \Example 2, using 1.886 g. of3,3-bis- (aminomethyD-oxetane, 160 cm? of dimethylformamide and 58.5 g.of prepolymer solution. A limpid solution is obtained which is convertedinto a film as described in Example 1. This film has the followingcharacteristics:

Tensile strength611 kg./cm.

Elongation at break718% Force for 100% elongation-42.3 kg./cm.

Immediate residual elongation after 100% elongation- Softening point2l0C.

EXAMPLE 5 121.2 g. of polytetrahydrofuran of molecular weight 2020 and107 g. of toluene are introduced into a 300 cm. flask. 63.4 g. oftoluene are distilled to dehydrate the polyether. 22.2 g. of4,4'-diisocyanato-dicyclohexylmethane of 99% purity and 42.6 g. oftoluene are then introduced. The whole is heated for 2 hours underreflux with stirring. The stirring and heating are stopped, and 9.55 g.of 4,4- diisocyanato-dicyclohexylmethane and 20.8 g. of toluene are thenintroduced. The mixture is heated for minutes with reflux of the tolueneand stirring. After cooling, a prepolymer solution containing 0.0473% of--NCO groups per g. of solution is obtained.

55 g. of this prepolymer solution are run into a 250 cm. reactorcontaining 1.536 g. of 3,3-bis(aminomethyl)- oxetane of 98.2% purity andcm. of dimethylformamide; about of the prepolymer are added in 8 minutesand the remainder in 40 minutes. A limpid polymer solution of 17.4%concentration is obtained having a viscosity of 30 poises at 25 C. Afilm is prepared from this solution as in Example 1. The film has thefollowing properties:

Tensile strength-472 kg./cm.

Elongation at break660% Force for 100% elongation-33.4 kg./cm.

Immediate residual elongation after 100% elongation- Softening point-498C.

I claim: 1. A polyurethane block elastomer consisting essentially of mblocks of Formula I:

CHz-CHz UHF-CH1 CH-OHz-Cfi c H-NH-C 0- CHFC 2 zfiz and n blocks ofFormula II:

CHz-CH; CH -CH CH-CHz-CH CH-NH-C O UH -C GHQ-o with the proviso that theblocks of Formula H are separated from each other by the blocks ofFormula I, in which m and 11 represent integers from 20 to 400 andwherein OAO is a bivalent radical resulting from removal of the terminalhydrogen atoms from a terminal hydroxy macrodiol having a molecularweight of 700 to 5000 and a melting point below 80 C., the molar ratioof bis(aminocyclohexyl) methyl units to the total number of -O-AO unitsbeing from 1.5 to 3.011 and the molar ratio of bis(aminomethyl) oxetanylunits to the total number of -OAO units being from 0.5 to 2.0: 1.

2. An elastomer according to claim 1, in which the macrodiol is anu,w-dihydroxy-polyester.

3. An elastomer according to claim 2 in which the macrodiol is ana,w-dihydroxy-polyester obtained by esterification of a mixture of1,6-hexanediol and 2,2-dimethylpropane-1,3-diol, with adipic acid.

4. An elastomer according to claim 2 in which the macrodiol is anu,w-dihydroxy-polyester obtained by esterification of 1,2-ethanediolwith a mixture of adipic acid and azelaic acid.

5. An elastomer according to claim 1 in which the macrodiol is ana,w-dihydroxy-polyether.

6. An elastomer according to claim 5 in which the macrodiol ispolytetrahydrofuran.

References Cited UNITED STATES PATENTS 3,401,143 9/ 1968 Finelli et a1260-75 3,449,369 6/ 1969 Berezin 260-333 3,506,617 4/ 1970 Collardeau etal 26077.5

OTHER REFERENCES Nikolaev: Chem. Abstracts, vol. 70, 1969, 5249t.Campbell: Journal of Organic Chem., vol. 22, pp. 1029- 1035, 1957.

DONALD E. CZAJA, Primary Examiner E. C. RZUCIDLO, Assistant ExaminerU.S. Cl. X.R.

57140; 260-77.5 AM, 77.5 SP, 858 i

